We plan to prepare visual pigment analogs by combining opsin with cis retinaldehyde analogs which we have synthesized and purified. We plan to use the opsin-bound retinaldehyde analogs as probes of the rhodopsin chromophore binding site. The absorption and circular dichroism spectra of these analog pigments before and after irradiation may provide detailed information about the interaction between the chromophore and opsin in rhodopsin and in the intermediates resulting from photon absorption. Thus, we hope to learn something about the triggering events resulting from photon absorption that eventually lead to ionic events in the plasma membrane of the retinal rod.